SM 25x275 [2xM8] / N42 - magnetic separator

Strengths as well as weaknesses of NdFeB magnets.

Besides their remarkable pulling force, neodymium magnets offer the following advantages:

• They have unchanged lifting capacity, and over around ten years their attraction force decreases symbolically – ~1% (in testing),
• Neodymium magnets are remarkably resistant to demagnetization caused by magnetic disturbances,
• A magnet with a metallic silver surface is more attractive,
• They are known for high magnetic induction at the operating surface, which increases their power,
• Thanks to resistance to high temperature, they are able to function (depending on the form) even at temperatures up to 230°C and higher...
• Possibility of detailed shaping as well as adapting to complex applications,
• Universal use in modern industrial fields – they are utilized in HDD drives, electric drive systems, medical devices, and other advanced devices.
• Relatively small size with high pulling force – neodymium magnets offer impressive pulling force in compact dimensions, which allows their use in compact constructions

Disadvantages of NdFeB magnets:

• They are fragile upon too strong impacts. To avoid cracks, it is worth securing magnets in a protective case. Such protection not only protects the magnet but also improves its resistance to damage
• We warn that neodymium magnets can lose their power at high temperatures. To prevent this, we suggest our specialized [AH] magnets, which work effectively even at 230°C.
• Due to the susceptibility of magnets to corrosion in a humid environment, we suggest using waterproof magnets made of rubber, plastic or other material stable to moisture, in case of application outdoors
• Limited possibility of producing nuts in the magnet and complicated forms - preferred is a housing - magnet mounting.
• Health risk resulting from small fragments of magnets can be dangerous, in case of ingestion, which gains importance in the aspect of protecting the youngest. Additionally, small components of these magnets can disrupt the diagnostic process medical in case of swallowing.
• With mass production the cost of neodymium magnets can be a barrier,

Detachment force of the magnet in optimal conditions – what contributes to it?

Magnet power was determined for the most favorable conditions, assuming:

• using a plate made of low-carbon steel, serving as a magnetic yoke
• possessing a massiveness of min. 10 mm to ensure full flux closure
• with an ground contact surface
• without any clearance between the magnet and steel
• during pulling in a direction perpendicular to the mounting surface
• in neutral thermal conditions

What influences lifting capacity in practice

Bear in mind that the application force may be lower subject to the following factors, starting with the most relevant:

• Space between surfaces – every millimeter of distance (caused e.g. by veneer or unevenness) diminishes the magnet efficiency, often by half at just 0.5 mm.
• Pull-off angle – note that the magnet has greatest strength perpendicularly. Under sliding down, the holding force drops significantly, often to levels of 20-30% of the maximum value.
• Metal thickness – the thinner the sheet, the weaker the hold. Magnetic flux passes through the material instead of generating force.
• Metal type – not every steel attracts identically. Alloy additives worsen the attraction effect.
• Plate texture – ground elements guarantee perfect abutment, which increases force. Rough surfaces reduce efficiency.
• Thermal factor – hot environment weakens magnetic field. Exceeding the limit temperature can permanently damage the magnet.

* Lifting capacity was measured by applying a steel plate with a smooth surface of optimal thickness (min. 20 mm), under perpendicular pulling force, whereas under attempts to slide the magnet the holding force is lower. Additionally, even a minimal clearance {between} the magnet’s surface and the plate reduces the lifting capacity.